Introductory Algebra for College Students (7th Edition)

$4x(x-5)(x+5)$
$4x^{3}-100x\qquad$...factor out the GCF, $4x$. $=4x(x^{2}-25)\qquad$...recognize the difference of two squares: $a^{2}-b^{2}=(a-b)(a+b)$ $=4x(x-5)(x+5)$